How do you know if the airbags in your vehicle still work?

I have a 1997 truck that I still use so it is going on 17 years old. It has never been in a collision that required deployment of the airbags. How do I know they are still in working order? What is the estimated lifespan on airbags and their activation mechanisms? Anyone have any ideas?

Prompted by listening the report of General Motors non-disclosure of a years old problem while on the way to work today.